What is the study of fossilized pollen and spores called?

The study of fossilized pollen and spores is called palynology. More broadly, palynology examines microscopic, acid-resistant organic particles known as palynomorphs, including fossil and modern pollen, spores, and several kinds of microscopic marine organisms.

Pollen and spores are unusually valuable to scientists because their tough outer walls can survive in sediments for millions of years. By identifying the types and relative abundance of grains in a sediment layer, researchers can reconstruct ancient vegetation and infer past climates and environments. Palynology is therefore closely connected with paleobotany, geology, and paleoclimatology.

The field also helps correlate and relatively date sedimentary rock layers, especially when particular palynomorphs are associated with particular geological intervals. It has applications beyond fossils: archaeologists use pollen to reconstruct past landscapes and human plant use, forensic investigators can compare pollen traces from people or objects with locations, and melissopalynology identifies the botanical sources of pollen in honey. Stratigraphy studies rock layers, micropaleontology covers microscopic fossils more generally, and paleontology studies ancient life as a whole; each overlaps with palynology but is not the specific answer to this question.